/Engine/Source/Runtime/Analytics/AnalyticsET/Public/AnalyticsProviderETEventCache.h
Range checking is not done, similar toTArray. UseGetDefaultAttributeCount()first!
one attribute of the default attributes so we don't have to copy the entire attribute array.
[FAnalyticsEventAttribute](API\Runtime\Analytics\FAnalyticsEventAttribute) GetDefaultAttribute ( int32 AttributeIndex ) const